Folks, appreciate thoughts on this one. Got a 2.0D Volvo S40 saloon on a 59 plate. For the last few months a few times a week I will go to start the car and find the engine turns over no problem at all it appears to try and fire but dies immediatly, it may take up to a dozen turns of the key before the engine will actually fire. Other times it starts first times with ease.

What should I check here ????

Thank you for reading